Separator apparatus for engine air inlets



Oct. 20, 1970 H. 0. CONNORS 3,534,548

SEPARATOR APPARATUS FOR ENGINE AIR INLETS I Filed June 30. 1969 3Sheets-Sheet 1 INVEN TOR. HAROLD CONNORS Z; ATTORNEYS.

Oct. 20, 1970 H. D. CONNORS 3,534,548

SEPARATOR APPARATUS FOR ENGINE AIR INLETS Filed June 30, 1969 sSheets-Sheet 2 r JNVENTOR. I HAROLD D. CONNORS ATTORNEYS.

United States Patent 3,534,548 SEPARATOR APPARATUS FOR ENGINE AIR INLETSHarold D. Connors, Milford, Conn., assignor to Avco Corporation,Stratford, Conn., a corporation of Delaware Filed June 30, 1969, Ser.No. 837,395 Int. Cl. F02c 7/04 US. Cl. 6039.09 Claims ABSTRACT OF THEDISCLOSURE This disclosure describes an apparatus for attachment to agas turbine engine for separating and removing foreign particles fromthe engine air supply. The separator provides separate primary andsecondary airpaths which are combined in a main flow path upstream ofthe engine inlet. An expansible dam is positioned in the primary airpathfor preventing flow in the primary path during periods of separatorutilization. During periods of separator utilization, all engine air isdrawn through the separator and cleaned air from the separator entersthe engine inlet. Particle contaminants are removed from the airstream.Anti-icing means are also provided in the separator.

BACKGROUND OF THE INVENTION This invention relates to a contaminantseparator for use adjacent the air inlet to a gas turbine engine, andmore patricularly to a separator apparatus for removing foreign mattersuch as sand and dust from the airstream.

Aircraft turbine engines are particularly susceptible to damage fromforeign objects introduced into the air intake stream of the gas turbineengines. Stones, gravel and other foreign matter drawn into theairstream often rupture, distort, and damage blades and other componentparts of the engine. These particles, which individually have littleeffect on the engine, can cause very substantial damage when introducedinto the engine in large quantities. For example, it has been found thatthe engine of a helicopter operating at low altitude in a desertenvironment can lose performance due to erosion of engine blading byhigh velocity sand particles. In addition, the desired balancedcondition of the compressor is often disrupted and the useful life ofthe engine shortened, if it is not completely destroyed.

The importance of removing small foreign particles, such as sand anddust, has long been recognized. Many mechanisms for accomplishing thispurpose are known in the art. One example is the separator shown in US.Pat. 3,371,471 to H. D. Connors and assigned to Avco Corporation.However, the present invention provides certain improvements recognizedas important. Some improvements and advantages of the present inventionare the self-cleaning capability, minimal maintenance requirements,compact, lightweight, accessible, small volume of carrier air, lowpressure loss, small amount of power required to eject contaminant andeffectiveness over a broad range of particle size from full design flowto flow.

Accordingly, it is an object of this invention to provide a lightweightand compact separator for effectively removing contaminant from theairstream supplied to a gas turbine engine.

A further object of this invention is to provide a sepa rator with theabove-mentioned advantages.

SUMMARY OF THE INVENTION This invention provides an improved contaminantseparator for removing contaminants from the stream of air supplied tothe inlet of a gas turbine engine. The separator utilizes centrifugalforces acting on the contaminants in the separating stations to extractthe contaminant from the stream of air. Cleaned air from the separatingapparatus is in communication with the main airstream and reenters theairstream upstream of the engine air inlet. Means are provided forpreventing airflow in the primary airpath during periods of separatorutilization.

Other details, uses, and advantages of this invention will becomeapparent as the following description of the exemplary embodimentsthereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show presentexemplary embodiments of this invention in which:

FIG. 1 is a vertical section, partially in cross-section, through theseparator assembly in a vertical plane and showing the enginetransmission and drive shaft fairing extending forward of the annularair inlet to the engine;

FIG. 2 is a cross-sectional view showing the inflatable dam andanti-icing means;

FIG. 3 is a diagrammatic representation of a dual-stage cyclonicseparating station used in the present invention;

FIG. 4 is a diagrammatic representation of another embodiment of thepresent invention utilizing a threestage cyclonic separating station;and

FIG. 5 is a diagrammatic view of another exemplary embodiment showingmultiple inlet channels.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT Reference is now made to FIG.1 which illustrates one exemplary embodiment of the improved contaminantseparator of this invention, which is designated generally by thereference numeral 10. The separator assembly 10 is designed for mountingon the front of a gas turbine engine 12, having an annular air inlet 14and a forwardly extending engine transmission and drive shaft fairing16. The forwardly extending fairing 1 6 may have varying configurationsdepending on whether the engine is a turboprop, geared helicopter, highspeed helicopter, or turbofan version and the present showing is only anexemplary embodiment.

The specific structure illustrated in FIG. 1 is a crosssection of anannular separator assembly 10 with the longitudinal axis of the fairing16 or the axis of the engine as a centerline. The separator assembly 10is cantileverly mounted to the inlet fairing 18 by suitable means suchas bolts 17 which provide for easy attachment and removal of theseparator 10. The separator assembly 10 comprises an annular outerhousing member 20 and an inner housing member 21 within which is mountedmeans 22 for removing contaminant from the airstream as will beexplained herebelow.

The separator assembly 10 defines two separate flow paths which combineinto a main flow path 24 upstream of the engine inlet 14. The twoairpaths are defined as a primary axial flow path 26 and a secondaryflow path 28. During normal operation of the engine, the majority of theairflow is through the primary airpath 26 to the main flow path 24 andthen to inlet 14 with a small portion of secondary air being drawnthrough the secondary airpath 28.

An inflatable boot or dam member 30 is mounted to the inner housing 21adjacent the primary airpath 26. The expansible boot 30 has anunexpanded position shown in solid line and an expanded position shownin phantom line. When the boot 30 is in the unexpanded or retractedposition, the primary airpath 26 is not obstructed and air can flowtherethrough to the main airpath 24 and engine inlet 14. However, whenthe inflatable boot 30 is in the expanded position, it forms a dam orcomplete obstruction in path 26 since the boot inflates until it touchesor 3 engages fairing 16, thus preventing any airflow through the primaryairpath 26. In the boot expanded condition, all air supplied to theengine inlet 14 is drawn through the secondary airpath 28 and will becleaned by the separator assembly 10.

As best seen in FIG. 2, the inflatable boot 30 is in communication witha compressor inlet vacuum source (not shown) and a compressor pressuresource (not shown). Suitable means such as tubing or conduit 32 connectsthe boot 30 with a valve 34. Conduits 36 and 38 connect the valve 34with the compressor inlet vacuum source and the compressor pressuresource, respectively. Thus, to inflate the boot 30, valve 34 isenergized such that the vacuum source conduit 36 is cut off and the boot30 is directly in communication with the pressure source conduit 38. Todeflate or retract boot 30, the valve is deenergized so as to shut offthe pressure source and vent the boot to the vacuum source so that boot30 is in communication with the compressor inlet vacuum source conduit36.

As seen in FIG. 1, an annular curved wall 40 extends from the housing 20radially inward and terminates closely adjacent a catching lip or wall42 which is attached to the housing 20 along the interior side. A formedwall 44 is attached to the inlet fairing 18. Walls 40 and 44 and the lip42 define the secondary airpath 28. Thus, air containing contaminantsuch as sand and dust passing through the secondary airflow is initiallyaccelerated and then drawn through a turn. The contaminant is deflectedonto the outer flow wall 40 because of the centrifugal forces acting onthe contaminant particles. The contaminant particles are prevented fromcontinuing to the engine inlet 14 by the catching lip 42.

Side splitter vanes 29 may be mounted in the inlet to the secondaryairpath 28 to prevent a tangential contaminant path and to guide thecontaminant particles to improve the separator effectiveness. It hasbeen found that approximately 90% of the air is initially drawn into theengine inlet passage while of the air is caught by wall 42 and passesthrough passage 46 as carrier or transport air for the contaminant.

The termination edge of flow Wall 40 and catching lip 42 define apassage 46 which is in communication between the secondary flow path 28and the means 22 for removing the contaminant from the airflow. Thus,contaminant and carrier air from secondary path 28 is deflected by'lip42 through passage 46 to a chamber 48 which is upstream of thecontaminant removing means 22.

The contaminated air from chamber 48 passes through a series ofcentrifugal cleaning stations. Each cleaning station comprises aplurality of cyclonic or vortex type separating tubes which operate in awell-known manner. As an example, the contaminant laden air is admittedpast inclined guide blades or through a tangential inlet into a chamber,called a cyclone chamber whereby the air is set spinning therein and bythe centrifugal force thus engendered concentrates the particles towardthe periphery of the cyclone chamber. The concentrated particles aredischarged at the periphery of each chamber and the particleorcontaminant-free air passes on straight through the cyclone separator.

The operation of the series or system of cleaning stations is bestdepicted in the diagrammatic representation of FIG. 3 Where it is seenthat the contaminated air passes from chamber 48 to a first bank ofcyclonic separator tubes 50 where the contaminant is removed as abovedescribed. It is also noted that about 10% of the air passingtherethrough is discharged as contaminant carrier air.

In this description, dashed arrows represent the contaminant and carrierair while plain arrows represent the clean air. r,

In order to have the cleaning system operate, it is necessary to backpressure the tubes 50 by restricting the discharge of the tubes. This isaccomplished through the use of a fine mesh screen or similar device 60!Thu clean air from tubes 50 is transmitted through screen 60 to acleaned air passage 52 and reenters the secondarry airpath 28 to combinetherewith upstream of the engine inlet 14. Contaminant from the primarytubes 50 plus a small percentage of carrier or transport air,approximately 10% of the air passing through tubes 50, is transmitted toa second cleaning station bank having a fewer number of cleaning tubes54 for further cleaning and separation. Clean air from the second bankof tubes is also trans mitted through the passage 52 for reentry intothe secondary airpath. Inasmuch as the second bank of cleaning tubes isthe final separation step, the cleaned air from tubes 54 need not passthrough a back pressuring screen but is transmitted directly into thepassage 52. Back pressure is not needed at this stage of the cleaningsystem. The motivating power required to draw the air and contaminant ofthe secondary air system through the separator 22 is the velocity headat the engine inlet.

Concentrated contaminant from the second bank of cleaning tubes may beeither accumulated in a storage chamber or dumped overboard by anyconvenient method such as the use of one or more contaminant airejectors 56 (FIG. 1) which receives a source of high pressure air fromthe compressor for ejecting the contaminant through an ejection tube 58to the atmosphere.

The separator assembly 10 incorporates an anti-icing arrangement whichoperates in a normal manner. As seen in FIG. 2, the leading and interiorsurfaces of the separator define anti-icing passages 62 and 63 which arein communication, through conduits 64 and 65, with the ducts (not shown)normally supplying anti-ice hot air to the air frame/engine air inletfairing. Thus, during icing conditions engine bleed air is transmittedthrough conduit 64 to passages 62 to prevent icing of the separatorassembly 10.

To protect the engine from the effects of grass, etc., and large foreignobject damage, a large area screen, perforated plate, louvered intake,or similar device 66 is used. The screen is attached to the separator inany known manner.

FIG. 4 is a diagrammatic representation of another embodiment of theremoval means 22 in which a threestage cyclonic separator assembly isutilized instead of the two-stage assembly as illustrated in FIG. 3. Theoperation of the three-stage assembly is identical with the operationabove described in the two-stage. Contaminated air enters the first bankof primary tubes 68 and cleaned air 70 passes through the back pressurescreen 72 for reentry into the secondary flow path 28. The contaminantplus carrier air from the tubes 68 is transmitted to a bank of secondarytubes 74 for a secondary cleaning and contaminant separation. Cleanedair 76 passes from the secondary tubes 74 through a back pressurerestricting screen 78 for reentry into the secondary airpath 28. Thecontaminant from the secondary tubes plus the small amount of carrierair is transmitted to the third stage or tertiary tubes 80 for finalcleaning and separation. Cleaned air 82 passes from the tubes 80 fordirect reentry into the secondary airpath 28 and concentratedcontaminant 84 from the tubes 80 is transmitted for either accumulationor ejection overboard. It should be noted that the staged cyclonicseparator cleaning assembly can have any number of cleaning stages orbanks of tubes. The system will operate as long as each preceding stageis back pressured and the contaminant is transmitted to the inlet of thenext stage. The final cleaning stage is not back pressured.

Another exemplary embodiment of this invention is illustrated in FIG. 5of the drawings. The separator assembly illustrated in FIG. 5 is verysimilar to the separator assembly 10; therefore, such separator assemblywill be designated generally by the reference numeral 10A and parts ofthe separator assembly 10A which are very similar to corresponding partsof the separator assembly 10 will be designated by the same referencenumeral as separator assembly also followed by the letter designation Aand not described again. The main difference between the separatorassembly 10A and the separator assembly 10 is in the secondary airpath.In this embodiment, the secondary airpath is comprised of multi-channels28A and 28B. It is seen that channel 28B is axially displaced relativeto the channel 28A. Each channel has a catching lip 42A and 42B forcatching and deflecting contaminated air into the separator chamber 48A.For purposes of this explanation, the conduits or ducts connectingcatching lip 42B and chamber 48A are not shown. The contaminated airpasses from chamber 48A to the first bank of cyclonic separator tubes50A which are back pressured by screen A. Contaminated air from tubes50A is transmitted to the second cleaning stage, comprising a pluralityof cleaning tubes 54A for further cleaning and discharge as previouslydescribed. The inflatable boot 30A prvents air from passing through theprimary passage 26 when the separator is in the operational mode. Itshould be noted that any number of secondary air channels may beutilized. In addition, each of the channels is connected individually orin common with the contaminant removal means. One advantage of themultichannel separator is to reduce the overall pressure loss during theoperational or separating mode.

The principle of operation is that during a sand ingestion environmentthe inlet dam is inflated to block off the normal air passage to theengine. Blockage of this channel causes the engine to now pass throughthe inlet louvered screen and traverse a turn. The air and sandparticles are initially accelerated, then they are slung to the outerWall by their inertial force as the airflow is decelerated and turnedover 90. The particles impinge on the channel outer wall that iscontoured to control the ricochet angle of the particles so that theybounce and flow into the sand catching lip mounted on the channel outerwall. Approximately 10% of the initial inlet air flowing through thesecondary airpath is used as a carrier medium for the sand. About 90% ofthe carrier air at every cleaning stage is returned to the secondaryairpath for transmission to the engine inlet. The suction head availableat the engine inlet face is the motive power for the carrier air. Thesand may be deposited in the lower section of the separator and eithercollected or damped overboard by means of a pump, blower, gravity orventuri device. The louvered inlet protection screen is an aid inpreventing large objects, grass, etc., from entering the engine intake.The screen area may be large to mini mize pressure loss.

During normal operation outside a sand and dust environment the inletdam is retracted and a normal path is resumed to the engine.

It should be noted that during the normal operating conditions some airwill be drawn through the secondary airpath although the primary airflowis through the primary axial flow path. It can be seen that theseparator assembly will be in reduced operational mode, due to the smallairflow in the secondary airpath, during conditions when the inflatableboot is in the retracted position.

It is noted also that in the preferred form of the invention shown theparts are annular to conform to the engine inlet position andconfiguration, although important features of the invention could beaccomplished by rectangular or other shaped parts having substantiallythe same general cross-section as shown.

It can be seen that this invention presents advantages not heretoforeincorporated in separators for gas turbine engines. Less than 1% of theinitial main airstream is lost in cleaning steps. Thus, this inventionprovides a separator which is of simple and economical construction, iscompact and provides for minimum maintenance.

While a present exemplary embodiment of this invention has beenillustrated and described it will be recognized that this invention maybe otherwise variously embodied and practiced by those skilled in theart.

What is claimed is:

1. In a gas turbine engine assembly including a compressor having aninlet thereto and a main airflow path directed to the inlet, acombustor, and a turbine in serial flow arrangement, a contaminantseparator assembly for removing contaminant from a stream of airsupplied to the compressor inlet, said separator comprising:

a housing assembly mounted ahead of the compressor inlet and defining aprimary axial flow path and a secondary flow path, said paths beingcombined in a main airflow path upstream of the compressor inlet,

expansible means mounted in said housing adjacent the primary flow path,said expansible means having an unexpanded position and an expandedposition, said expansible means permitting axial flow through saidprimary airpath in the unexpanded position and said expansible means inthe expanded position obstructing the primary airpath to prevent flowtherethrough wherein air supplied to the engine inlet is all drawnthrough the secondary airpath,

means for expanding said expansible means to said expanded position andfor deflating said expansible means to said unexpanded position,

contaminant removal means mounted in said housing for removingcontaminant from air flowing therethrough,

said contaminant removal means being in communication with saidsecondary airpath and further defining a third flow path downstream ofthe contaminant removal means, and

said third airpath being in communication with the main airflow path,wherein air and contaminant transmitted to the contaminant removal meansfrom the secondary airflow path will be acted on by said contaminantremoval means whereby contaminant is removed from the airstream and thecleaned air is transmitted through the third flow path for reentry intothe secondary flow path upstream of the compressor inlet.

2. A contaminant separator as set forth in claim 1 in which:

said contaminant removal means comprises a plurality of cleaning stages,each of said stages including cyclonic separator tubes wherein clean airis transmitted to said third flow path and contaminant is transmitted tothe next cleaning stage for further cleaning.

3. A contaminant separator as set forth in claim 1 in which saidcontaminant removal means comprises first and second cleaning stages,

said first stage comprising a plurality of cyclonic tubes incommunication with said secondary flow path for receiving contaminatedair therefrom wherein cleaned air from said cyclonic tubes istransmitted to said third flow path and contaminant is transmitted tosaid second cleaning stage, and

said second stage further comprising a plurality of cyclonic tubeswherein cleaned air therefrom is transmitted to said third flow path andconcentrated contaminant is accumulated in a collection chamber.

'4. A contaminant separator as set forth in claim 3 in which:

an ejector means is mounted within said collection chamber and incommunication with said cyclonic tubes wherein concentrated contaminantfrom said cyclonic tubes is ejected overboard to atmosphere,

said expansible means comprises an inflatable boot, and in which saidmeans for inflating and deflating said inflatable booth furthercomprises:

a conduit connecting said inflatable boot with the compressor inletvacuum source and compressor pressure source,

a switching valve connected in said conduit between said boot andcompressor wherein the inflatable boot is connected to the compressorpres- 7 sure source for inflation and the inflatable boot is connectedto the compressor inlet vacuum source for deflation.

5. A contaminant separator as set forth in claim 4 further comprising:

a screen mounted over said secondary airpath for preventing largeforeign objects from entering the secondary airpath, and

anti-icing passages mounted in said housing, said passages being incommunication with the engine bleed air wherein engine bleed airflowthrough the pas sages will prevent icing of the separator assembly.

6-. In a gas turbine enginge assembly including a compressor having aninlet thereto and a main airflow path directed to the inlet, acombustor, and a turbine in serial flow arrangement, a contaminantseparator assembly for removing contaminant from a stream of airsupplied to the compressor inlet, said separator comprising:

an annular housing assembly having concentric inner and outer wallmembers, said assembly being cantilever mounted ahead of the compressorinlet and defining a primary axial flow path adjacent the inner wall,said housing assembly further having an annular curved wall surfaceextending from the outer wall radially inward and terminating closelyadjacent the inner wall,

a formed annular member mounted to the engine inlet in cooperativerelationship with said annular curved wall surface to define a secondaryflow path, said secondary flow path being in communication with saidprimary axial flow path wherein said flow paths are combined in a singlemain airflow path for transmission to the compressor inlet,

an annular catching lip member spaced from the terminating end of saidannular curved wall surface and extending into said secondary flow pathsuch that air being drawn through the secondary airpath is drawn througha turn wherein centrifugal forces acting on the contaminants cause thecontaminants and a small amount of carrier air to be deflected onto saidannular curved wall surface and directed to said catching lip member,

a plurality of contaminant removal stages in serial flow arrangementmounted in said housing, each of said stages comprising a plurality ofcyclonic separator tubes, said first stage being in communication withsaid secondary flow path wherein contaminant and carrier air caught bysaid catching lip member is transmitted to said first contaminantremoval stage,

each of said contaminant removal stage being in communication with saidsecondary flow path downstream of said catching lip member whereincleaned air from each of said removal stages reenters the secondary flowpath for transmission to the compressor inlet;

an annular inflatable boot mounted in said housing adjacent the primaryflow path, said boot having an unexpanded position and an expandedposition, said boot permitting axial flow through said primary flow pathin the unexpanded position and said boot in the expanded positionobstructing the primary flow path to prevent flow therethrough whereinduring periods of boot inflation the air supplied to the compressorinlet is all drawn through the secondary flow path and contaminantremoval stages, and means for expanding said inflatable boot to saidexpanded position and for deflating said inflatable boot to saidunexpanded position.

7. A contaminant separator assembly as set forth in claim 6 in which thecontaminant and carrier air from each stage is transmitted to the inletof each succeeding stage, and ejector means in communication with thefinal stage wherein concentrated contaminant from the final stage isejected overboard.

8. A contaminant separator assembly as set forth in claim 7 furthercomprising:

a screen mounted over said secondary airpath for preventing largeforeign objects from entering the secondary flow path, and

anti-icing passages mounted in said housing, said passages being incommunication with the engine bleed air wherein icing of the separatorassembly may be prevented thereby.

9. A contaminant separator as set forth in claim 1 in which said housingassembly further defines a plurality of secondary fiow paths, each ofsaid secondary flow paths being in communication with said contaminantremoval means wherein air and contaminant passing through each of saidsecondary flow paths will be acted on by said contaminant removal means.

10. A contaminant separator as set forth in claim 9 in which eachsucceeding secondary flow path is axially displaced relative to thepreceding flow path, each of said secondary flow paths being incommunication with said primary axial flow path wherein all the flowpaths are combined in a main air flow path upstream of the compressorinlet.

References Cited UNITED STATES PATENTS 2,600,302 6/ 1952 Kinsella.3,302,396 2/ 1967 Robbins. 3,347,496 10/1967 Opfer 24453 CARLTON R.CROYLE, Primary Examiner US. Cl. X.R.

